SPID#: 55 Paternity was determined for 78 sooty mangabeys (Cercocebus torquatus atys), born from 1986 to 1993, using a DNA profile analysis. This analysis was based on two independent assays of the genome of each individual using multilocus DNA probes. The mangabeys were descendants of 28 individuals acquired in 1968 and were members of either a large breeding group (n=98) or a smaller group (n=18). The small group was studied only to assess the relationship between dominance rank and reproductive success. A significant correlation was found between dominance rank and reproductive success in both the large and small groups, although the effect was more pronounced in the smaller group. There was also a significant correlation between mounts and the number of surviving offspring each male sired in one birth year. The same male did not always sire the offspring of a given female from year to year. Behavioral data focusing on male-offspring interactions found that offspring (n=15) did not preferentially affiliate with their sire and that males affiliated with infants too infrequently for analysis. Additionally, there was some evidence for incest avoidance. Thus, this study of a large sooty mangabey colony demonstrates that 1) dominance rank is a predictor of reproductive success; 2) there is no preferential attraction for one's own offspring by males or one's own sire by offspring; 3) the same male generally does not sire the offspring of a given female year to year and 4) incest avoidance may be operating.